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accuracy. In Vertebrates, however, the cleavage is much 
more indeterminate and the relatively equal size of the 
cleavage-cells and their great number, when differentiation 
sets in, very soon make it impossible to find out any longer 
the place ot the animal pole, where the first two cleavage- 
furrows have intersected. Thus we must look for another 
landmark, or make it ourselves, to enable usto determine 
the place of the animal pole. The egg of the anchovy 
(Engraulis encrasicholus) presents certain advantages in 
this respect. It is characterized by its oblong shape in 
which it reminds one of the eggs of Cephalopods. It agrees 
Fig. 33. Three stages of development of the egg of the anchovy 
(Engraulis encrasicholus), b and c after WENCKEBACH, 1886. 
a morning of the Ist day, b morning of the 2nd day, c 
evening of the 2nd day. 
Ch notochord, m micropyle, of auditory vesicle, pol polar 
odies. 
with the latter also in that after fertilization the animal 
pole, with the nucleus and an accumulation of protoplasm, 
Is situated at one of the extremities of the unsegmented 
germinal disc extends ina concentric way over the surface 
of the egg, the circular circumference during this process 
